Project Summary Glaucoma is a leading cause of blindness and affects over 60 million people worldwide. The mechanisms underlying glaucoma have been studied extensively but are not yet fully understood. We recently reported the first evidence that Schlemm?s canal (SC) expresses Prox-1, the master control gene for lymphatic development. The endothelial characteristics of SC has been debated for a long time. Regardless of its being considered as a blood, lymphatic, or intermediate vascular type, in this proposal, we will apply our knowledge and experience with lymphatic and blood vascular research to investigate SC, a critical structure of the conventional outflow pathway of aqueous humor that regulates intraocular pressure (IOP). IOP elevation is the primary and most important risk factor of glaucoma. Our long-term goal is to elucidate the underlying mechanisms governing SC function using various in vivo ocular hypertension models and in vitro SC cell culture systems, a necessary prerequisite to the development of new therapeutic protocols. Our main hypothesis is that Wnt pathway plays a critical role in SC, and its intervention can modulate IOP and treat glaucoma. This proposal is based on a large amount of preliminary data and the most recent advances in technology. Our specific aims are: 1) investigate the specific role of Wnt pathway in SC cells in vitro using human SC cell culture system and small interfering RNAs (siRNAs); 2) explore the specific role of Wnt pathway in SC in vivo using conditional knockout mice, ocular hypertension model, and advanced live imaging technology; and 3) assess the effect of Wnt pathway intervention on ocular hypertension and glaucoma using ocular hypertension models and optical coherence tomography (OCT). Our study promises for revealing novel mechanisms and therapeutic strategies for ocular hypertension and glaucoma, and possibly other vascular-related diseases in the body.